1. Technical Field
The present invention relates to an image forming device and method, more particularly, to an image forming device such as a laser printer for forming an image on a recordable medium with image data supplied from a document. The device provides an optimum print quality by varying the fixing temperature of a fixing unit after presuming an amount of consumed toner.
Moreover, the present invention relates to an image forming device and method capable of supplying otpimum print quality by varying the transferring voltage level of a transfer unit after presuming the amount of consumed toner.
2. Related Art
In an electrophotographic image forming device, such as a copier, a color copier, a color printer, an optical density device, etc., a charging roller rotates and evenly charges a photosensitive body which is spread over the outer periphery of a photosensitive drum provided with a high voltage.
The charged photosensitive body forms an electrostatic latent image by means of a laser beam transmitted from an exposing unit (i.e., a light source of a laser diode) which converts a digital signal into the laser beam.
At this time, the electrostatic latent image formed at the photosensitive drum is developed by toner passing through a developer and changed to a visible image. This visible image is transferred onto the recordable medium, which is transported and fed by a pickup roller, and thereby an image is formed. The image transferred onto the recordable medium is fixed onto the recordable medium by heat and pressure of a fixing unit and then outputted.
When power is supplied to the image forming device, a warm-up is performed with predetermined timing according to the characteristic of the device. After completing the warm-up, an on line mode capable of performing a print command is set. When the print command is not received in the on line mode during a preset time, the device is returned to a standby mode. When the print command is received in the standby mode, the printing operation is performed after passing through the warm-up phase.
The image forming device is designed to control the fixing temperature according to the kind of recordable medium and not the transferred toner amount.
Moreover, since the transferring voltage level is properly set, a proper amount of toner is transferred onto the recordable medium without regard to the amount of transferred toner.
The aforesaid image forming device has the following problems.
First, in fixing the toner transferred onto the recordable medium, the fixing temperature of the fixing unit is not controlled by the toner amount transferred onto the recordable medium. Instead, the fixing temperature varies according to the kind of recordable medium, such as normal paper or transparent paper. When a large amount of toner is transferred onto the recordable medium, an offset of the fixing temperature relative to the amount of consumed toner is generated in the fixing unit, thereby degrading the print quality.
Second, in transferring the toner onto the recordable medium, since the electric potential of the transferring voltage is predetermined, when a large amount of toner is transferred onto the recordable medium, the poor transfer of toner is generated, and thereby the print quality is degraded.